Grant Shapps, using the name Michael Green, told audiences in 2007 that they could 'make $20,000 in 20 days guaranteed or your money back' if they bought his software. Photograph: Steve Back/Barcroft Media

Labour is calling for police to press ahead with an investigation for possible fraud and copyright violations into the family business founded by the Tory chairman Grant Shapps – for selling software that inflates a website's advertising revenue by copying other people's content – as many of its web pages have disappeared from the internet.

The opposition had been pressing for the Metropolitan police to launch an investigation into How To Corp, an internet marketing firm set up by Shapps and his wife in 2005, which through its website sells "autoblogging" software that creates an instant cashflow by allegedly plagiarising information. Earlier this week Steve McCabe, a Labour MP, wrote to the lead officer in the specialist crime and operations division dealing with the case to warn that five months after his original complaint "How to Corp appears to have taken down many of its web pages, thus making it harder for any investigation to be conducted".

How To Corp created a product, TrafficPaymaster, that McCabe says seems to be specifically designed to "circumvent the rights of copyright-holders". The software creates content for web pages by "scraping" content from other websites – which Labour says means "copying it and using it without permission in the process of running a business". The company could be prosecuted, suggests McCabe, for "possible offences committed against the Copyright, Designs and Patents Act 1988, as well as conspiracy and obtaining a pecuniary advantage".

The Guardian first revealed that How To Corp's premier product – a $497 (£313) software package, TrafficPaymaster – created web pages by "spinning and scraping" content and sought to attract advertising, in contravention of Google's code of conduct. In response Google said it would blacklist sites created by TrafficPaymaster.

McCabe, who has the blessing of the party's high command to pursue the Tory chair, has also got hold of a TrafficPaymaster user manual and presents this as fresh evidence to be considered by the police. "If you note the properties on the document, you will see the author is 'Grant'. This may add further weight to the contention that the document was authored by Grant Shapps MP."

A spokesperson for the Met said the force was "still assessing an allegation relating to the breach of copyright. There is no investigation at the moment."

Last year Shapps told the Guardian the company was conceived as a partnership between his wife and himself in 2000, although it was first registered as a company five years later. Going under the name Michael Green and casting himself as an internet marketing guru, Shapps in 2007 claimed audiences could "make $20,000 in 20 days guaranteed or your money back" – if they spent $200 buying his bespoke software.

A year later, in 2008, Shapps transferred his share of the company to his wife, Belinda, and the Tory chair says he has nothing to do with the firm. Michael Green has been replaced by Sebastian Fox as the face of the company – although the two pseudonyms appear interchangeable. Shapps said TrafficPaymaster was created two years after he left the company, which is now run by his wife.

A Conservative party spokesperson said: "Rehashing a baseless six-month-old story is a sign of utter desperation by Labour. Ed Miliband should apologise for allowing his MPs to waste valuable police time with this politically motivated letter and instead focus on coming up with some credible policies."